Using two NASA X-ray satellites, astronomers have discovered what
drives the "heartbeats" seen in the light from an unusual black hole
system. These results give new insight into the ways that black holes
can regulate their intake and severely curtail their growth.

This study examined GRS 1915+105 (GRS 1915 for short), a binary system
in the Milky Way galaxy containing a black hole about 14 times more
massive than the Sun that is feeding off material from a companion
star. As this material falls towards the black hole, it forms a
swirling disk that emits X-rays. The black hole in GRS 1915 has been
estimated to rotate at the maximum possible rate, allowing material in
the inner disk to orbit very close to the black hole, at a radius only
20% larger than the event horizon, where the material travels at 50%
the speed of light.

Using the Chandra X-ray Observatory and the Rossi X-ray Timing
Explorer (RXTE), researchers monitored this black hole system over a
period of eight hours. As they watched, GRS 1915 gave off a short,
bright pulse of X-ray light approximately every 50 seconds, varying in
brightness by a factor of about three. This type of rhythmic cycle
closely resembles an electrocardiogram of a human heart -- though at a
slower pace.

"Trying to understand the physics of this 'heartbeat state' is a
little like trying to understand how a person's heart beats by
watching changes in the blood flow through their veins," said Joey
Neilsen, a graduate student at Harvard University, who presented these
results from his dissertation at the American Astronomical Society
(AAS) meeting in Seattle, Wash.

It was previously known that GRS 1915 can develop such heartbeats when
its mass consumption rate is very high. After monitoring it with the
special combination of Chandra and RXTE, Neilsen and his collaborators
realized that they could use the pulses to figure out what controls
how much material the black hole consumes.

"With each beat, the black hole pumps an enormous amount of energy
into its surroundings," said Neilsen. "All that energy has profound
consequences for the disk, even very far from the black hole."

Changes in the X-ray spectrum observed by RXTE during each heartbeat
reveal that the inner region of the disk, at only a few times the
radius of the black hole's event horizon, emits enough radiation to
push material away from the black hole. Eventually the disk gets so
bright and so hot that it essentially disintegrates and plunges
towards the black hole. Then the cycle begins again.

"This behavior is a clear and startling demonstration of the power of
radiation in the fight against gravity," said co-author Ron Remillard
of the Massachusetts Institute of Technology. "During the heartbeat
state, radiation prevents the black hole from ingesting as much
material as it would otherwise."

Neilsen and his colleagues estimated that the rate at which material
falls onto the black hole changes by about a factor of ten during each
cycle, with the maximum rate coinciding with the X-ray pulse. Between
pulses, the inner part of the disk refills from material farther away
from the black hole.

The astronomers also used Chandra's high-resolution spectrograph to
study the effects of this heartbeat variation on regions of the disk
very far from the black hole, at distances of about 100,000 to a
million times the radius of the event horizon. By analyzing the
Chandra spectrum, they found a very strong wind being driven away from
the outer parts of the disk. The wind changed significantly in just 5
seconds, nearly 100 times faster than has ever been seen in a wind
from a stellar-mass black hole.

The researchers concluded that the strong X-ray pulse from the inner
disk must heat the outer disk. This heating process launches a wind,
so that each new pulse drives more wind from the disk. The rate of
mass expelled in this wind is remarkably high, as much as 25 times the
maximum rate at which matter falls onto the black hole.

"All that energy blows away an enormous amount of matter, equivalent
to one third the mass of the Moon per day! This effectively forces the
black hole onto a severe diet, and we think it eventually has real
consequences for the system's heartbeat," said co-author Julia Lee,
associate professor in the Astronomy department at Harvard and
Neilsen's thesis advisor.

This massive wind drains material from the outer disk and after a
couple weeks, this depletion affects the inner disk, causing the black
hole to feed much more slowly and its X-ray brightness to decrease
substantially. Unable to power such strong variations in the disk and
the wind, GRS 1915's 'heart' ceases to beat. This remarkable system
then likely begins one of its 13 other known patterns of variation.

Neilsen is a winner of the Roger Doxsey Travel Prize, which provides
graduate students within one year of receiving or receipt of their PhD
a monetary prize to enable the oral presentation of their dissertation
research at an AAS meeting.

Visitor Comments (10)

Adil, the nomenclature is as follows GRS stands for GRANAT source GRANAT is an earth orbiting observation platform from which the GRS 1915 105 was discovered, 1915 is the right ascension and 105 is declination.
The X-Ray source is a binary system composed of black hole and a star in common orbit, almost halfway across our galaxy. It emits X-Rays in a regular pattern, caused by the black hole accelerating matter drawn from the star.

Posted by Anon on Tuesday, 12.17.13 @ 04:29am

Always good to see discoveries such as this pushing the boundaries of scientific knowledge, but if my ECG looked that that, I'd ask a team to stand by with a defibrillator. Such analogy seems to make people draw odd conclusions.

Posted by Anon on Tuesday, 12.17.13 @ 03:45am

I love periodicity. Resonances of harmonic action from collision.

Posted by J. J. Madson on Friday, 05.13.11 @ 22:07pm

I do not believe in all my reading about these objects I ever ran across pulsating black holes. I have read so much maybe I have just forgotten, but all the same very educational as usual, something new learned.
I have a question for you Les, what do you mean by a living being? I would like to know what your thoughts on this is not to be arguing with you. Very interesting notion.
Marvin L. S.

Posted by Marvin L. S. on Saturday, 01.22.11 @ 17:11pm

Adil, GRS stands for Gamma Ray Source. Given that it is a compact object measuring as much as 14 times the mass of the Sun, astronomers suspect that it is a black hole.

Posted by Navneeth on Thursday, 01.20.11 @ 14:35pm

Is it just a "heartbeat" that makes one think of life? I see a visual connection to life when looking at the universe. As in microscopic sea life forms.

Posted by Roy Koch on Sunday, 01.16.11 @ 10:12am

Patrick, In the absence of any other forces, a black hole that isn't feeding off another star would keep spinning more or less forever.
Stephen Hawking predicted that black holes should evaporate very "slowly". For a black hole like GRS 1915+105 this evaporation will take trillions and trillions and trillions of times longer than the current age of the universe.
So basically, isolated, inactive black holes just sit there forever.

Posted by Joey Neilsen on Thursday, 01.13.11 @ 17:15pm

Very interesting report. I always suspected pulsating Black Holes, but could not explain to myself at what rate
this might happen.
Also of interest, the fact that there is not just an intake of material, but that at the rim of the disc there are winds expelling matter outwards.
But my real question is, what happens when the work of a Black Hole finishes? I mean what does a Black Hole turn to, once it has exhausted its activity? We know that at the core there is solidified matter that swirls at incredible speeds, does it just stop?

Posted by Patrick S. Selitrenny on Thursday, 01.13.11 @ 09:28am

What actually is this GRS 1915?

Posted by Adil on Thursday, 01.13.11 @ 02:05am

Appears that the term "Universe" needs to be rethought as new data leads one to believe that we exist within a living being.

Posted by Les on Thursday, 01.13.11 @ 01:36am

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